Machine for threading coil forms



Oct. 22, I946.

MACHINE FOR THREADING COIL FCRMS Filed April 3, 1943 3 Sheets-Sheet 1 INVENTOR S 8171021 If. Swpakoff s. H. STUPAKOFF 2,409,993

1946. s. H. S TUPA KOFF MACHINE FOR THREADING COIL FORMS Filed April 5, 19 43 3 Sheets-Sheet 2 43 45 .IL9fi5 I 1 47 L 4 35 INVENTOR SamonHSturakaff s. H. STUPAKOFF MACHINE FOR THREADING COIL FORMS Filed April 3, 1945 fLlgn.

3 Sheets-Sheet 5 INVENTOR semojzfiStgma/kaff Patented Oct. 22, 1946 MACHINE FOR THREADING COIL FORMS Semon H. Stupakofi', Latrobe, Pa., assignor to Stupakoff Ceramic & Manufacturing 00., Latrobe, Pa., a corporation of Pennsylvania.

Application April 3, 1943, Serial No. 481,705

7 Claims.

This invention relates to a thread cutting machine, and. especially to amachine for forming threads on the surface of a green .ceramic coil form.

Many types of coil forms, particularly those used for inductances in radio transmitting apparatus, are formed of ceramic material and must be threaded and drilled within quite close limits of accuracy. At present, the green ceramic coil forms are threaded by acutting tool which cuts a single thread at each revolution of the work piece, and the position where the thread begins and ends must be closely and accurately determined, The thread on the coil form is designed to receive turns of wire and, at suitable places, the coil formhas radial holes drilled therein through which terminals of the wire are passed. As the length of wire is critical, and the holes must be properly positioned with respect to the threads, the operation is one which has required care and skill.

The present invention provides a simple mechanism in which the complete threading operation is accomplished normally with but a single revolution of the work piece.

This is accomplished by providing a rotatable work holder with a thread cutting hob or comb positioned alongside of it to be moved into position to engage a work piece on the work holder. The number of cutting teeth on the hob or comb corresponds to the number of threads to be formed and cam means are provided thereby, with one revolution of the work piece, relative movement in an axial direction equal to the pitch of the desired thread takes place between the hob or comb and the Work piece. Where it is desired to slight- 1y extend the thread, as for example, to avoid any seam or blind spot, means is provided whereby slight additional movement may occur.

My invention may be readily understood by ref v erence to the accompanying drawings, in which:

Figure 1 is a side elevation of a machine embodying my invention;

Figure 2 is a transverse section in the plane of line II--II of Figure 1; 1

Figure 3 isa fragmentary view partly in side elevation and partly in longitudinal section of a modified form of mechanism;

Figure 4 is a transverse section in the plane of line IV--IV of Figure 3;

Figure 5 is a side elevation of still a further modification.

Figure 6 is a top plan view of a modification in which an abrasive wheel cuts the threads.

Referring first to Figures 1 and 2, 2 designates 2 a supporting bed on which is a head-stock 3 an a tail-stock 6; The head stock has a shaft 5 therein with a hand wheel 6 at the outer end thereof and a mandrel 6 at its other end over which a cylindrical core form.A is fitted. The mandrel may be of any known or preferred construction, such, for example, as that shown in my application Serial No. 468,411, filed December 9, 1942. Secured on the shaft 5 inwardly toward the head-stock from the mandrel is a disk 8 which is fast to the shaft to rotate therewith and which has a helical .cam surface 9 on its face.

The tail-stock 4 may have a retractable centering pin I 0 thereon, but this is by no means necessary. The tail-stock also carries a rod II which may be rotated by a handle I2 fixed thereto but which is fixed against longitudinal movement. Splined to the inner end of the rod II is a hob or cutter comb I3 which preferably comprises a cylindrical metal body having a thread I4 cut in the periphery thereof and from which a quadrant has been removed, as indicated at I 5.

When the quadrant is toward the work piece A, clearance is provided between the work piece and the cutter, enabling the Work piece to be put on and removed from the mandrel. When the shaft I I is rotated, a face of the quadrant may be turned to a position to cut into the periphery of the work piece. The thread I4 on the hob or cutter .corresponds to'the thread to be reproduced on the periphery of the work piece.

A spring I6 on the shaft II confined between the tail-stockfand the cutter or hob I3 urges the cutter or hob toward the left as viewed in Figure 1. On the end of the hob is a projecting pin I! that rides against the cam surface 9 on the disk 8. By reason of this arrangement, the cam will impart longitudinally travel to the cutter or hob I 3 as the shaft 5 is rotated to turn the work piece. The inclination of the cam 9 is equal to the pitch of the thread to be formed, so that with one complete revolution of the work piece the cutter will move relatively to the work piece the pitch of one thread.

The cam, mandrel and cutter are set up in predetermined relation for the work piece to be operated upon, so that when the Work piece is pushed onto the mandrel until it hits abutment pin it, the thread cutting operation will begin at a given distance from theend of the work piece and one complete turn of the work piece will normally conclude the thread cutting operation. The cutting of a quadrant from the periphery of the otherwise cylindrical cutter I3 not only provides an efficient cutter that may be easily sharpened from time to time, but provides clearance to e able the Work piece to be applied to and removed from the mandrel. The work piece is turned by turning the handwheel 6,

In some cases the thread may not be out entirely clean on one complete revolution or may not be quite continuous and fully developed at the point marking the normal beginning of the threading operation, which also is the point of ending after one complete revolution of the work piece, and to eliminate this a slight overtravel may be, in some cases, desirable. This can be accomplished in a number of ways and Figures 3 and 4 illustrate one way of doing it, and in these figures we have shown only a par-t of the machine. of Figure 1 which, but for the modification to be described, is the same.

In these figures, the head-stock 25 carries a shaft 21 similar to shaft 5 with a handwheel, not shown, at one end and a mandrel, not shown, at the other end. Splined on the shaft 2| is a cam member 22 similar to disk 8 with its cam surface 9. A spring 23,, bearing against the surface of the cam disk 22 and confined by a collar 24 constituting an abutment, urges the cam toward the left as viewed in Figure 3.

Around the shaft 2| in the head-stock 26 is a sleeve 25 having pins 26 projecting through slots 2'! in the head-stock. These pins are engaged in the arms 28 of a yoke-like lever having a handle 29, the arms being pivoted near the base of the head-stock. By moving the lever 29 back or forth, the sleeve 25, which bears against the end of the hub 22a of the cam member 22, may be moved back and forth along the shaft to effectively change the operating position of the cam relative to pin [1 on the cutter. Thus, after one complete turn of the work piece, the lever 29 may be moved toward the right a distance equal to one thread, after which the turning of the work piece may be continued for perhaps 1c, or to assure a slight overtravel of the cutter and clean any thread which is not sufficiently formed on one turn.

A spring detent under the handle 29 may engage notches 3| on the top of the head-stock for indexing and releasably holding the lever 29 for the desired increment of movement.

In the modification shown in Figure 5, there is shown a slightly different arrangement wherein the work piece is moved axially relative to the cutter 0r threading comb, instead of the comb being moved'with respect to the work piece. In this figure, 35 designates the bed of the machine on which is a head-stock 36 and a tail-stock or support 3'5. Mounted in the head-stock 56 is a shaft 38 which may rotate and which is also movable longitudinally. It is provided at its outer end with a handwheel 39. At the opposite end there is a mandrel 40 for holding the work piece A. The shaft 38 carries a collar 4| which constitutes an abutment for a spring 42, which spring bears against the inner end face of the headstock 35, tending to urge the shaft 38 toward the right as viewed in Figure 5. At the opposite side of the head-stock the shaft 38 is provided with a collar 43 having an inclined cam face A l thereon, the slope of which corresponds to the pitch of the thread which is to be cut. The headstock 35 is provided with a fixed pin 45 that bears against'the cam surface 44.

The support 31 is provided with a rotatable shaft 45 having a hand lever 41 by means of which it may be turned through a limited arc.

. 4 The shaft 46 is held against longitudinal movement. It carries on its inner end the threadcutting hob or cone 48, corresponding to the nection with Figure 1, after which the shaft 46 is turned to bring the cutter into engagement with the periphery of the work piece. The handwheel 39 is then rotated through one complete turn, and, as it rotates, the pin 45 bearing against the cam 44 causes the shaft with its work piece to travel longitudinally relative tothe threading 7 comb a distance equal to the pitch of the thread to be cut. In the modification shown in Figure 6, I have illustrated the threading comb as comprising a motor driven abrasive wheel with a serrated periphery. It may be used in an arrangement where either the comb or the work piece moves axially, but in Figure 6 the arrangement shown is similar to that of Figure 5 in which the work piece moves, and the cam for moving thework piece is not shown; In this figure, A is a work piece on a mandrel or shaft 50, similar to the shaft of Figure 5. The bed rails of the lathe are designated 5i, and 52 is a carriage with a crossfeed screw 53 for moving the tool post 54transversely. The tool post is of special form, carrying a small motor 55 driving a shaft 56 on which is a threading comb comprising an abrasive cylinder 51 with a series of teeth 58 on the periphery.

In use, the motor drives the abrasive comb at high speed. When it is operating, theyoperator moves the comb into engagement'withthe work piece. Then the work piece is rotated by hand, as previously described, and atthe-same time moves longitudinally the distance of the pitch of the thread. This threads the workpiece. The abrasive Wheel is then retracted and the work piece removed from the mandrel. The abraplaced face to face or it may be an integral body.

From the foregoing it will be seen that my invention provides a machine for threading green ceramic coil forms and the like very accurately and very rapidly and with assurance that the thread will be accurately formed over the desired portion of the periphery of the work piece.

While I have illustrated and described certain preferred embodiments of my invention/it will be understood that this is by way of. illustration and that various changes and modifications may be made therein within "the contemplation of my invention and under thescope of the following claims. i

I claim: i

1. A threading tool of the class described comprising a shaft having a mandrel thereon adapted to receive a work piece to be threaded,'a threading comb having a series of teeth corresponding in number and spacing to the number of threads to be formed on the work piece and to the pitch of such threads, a cam on the shaft having a cam surface equal to the pitch of one thread, means cooperating with the cam for imparting relative axial movement between the work piece and the comb equal to the pitch of a single thread, said comb being also movable into and out of position to engage a work piece on the mandrel, and manually operable means for changing the relative position between the cam and the work piece.

2. A threading tool of the class described comprising a shaft having a mandrel thereon adapted to receive a work piece to be threaded, a threading comb having a series of teeth corresponding in number and spacing to the number of threads to be formed on the work piece and to the pitch of such threads, a cam on the shaft having a cam surface equal to the pitch of one thread, means cooperating with the cam for imparting relative axial movement between the work piece and the comb equal to the pitch of a single thread, said comb being also movable into and out of position to engage a work piece on the mandrel, and

means for selectively changing the relation between the cam and the said cam-engaging means whereby the thread formed on the work piece may at the will of the operator be extended beyond that formed by a single turn of the mandrel.

3. A threading tool of the class described comprising a shaft having a work-holding mandrel thereon, means for turning the shaft, a cam on the shaft having a helical face, a thread-forming comb supported in work-engaging position alongside the mandrel, said comb having a series of thread-forming teeth thereon corresponding in number and spacing to the number of threads to be formed on the work piece and to th pitch of such threads, and means on the comb engaging the cam for moving the comb axially with reference to the mandrel when the shaft is rotated,

the helical face on the cam being equal to the pitch of a single thread.

4. A threading tool of the class described comprising a shaft having a work-holding mandrel thereon, means for turning the shaft, a cam on the shaft having a helical face, a thread-forming comb supported in work-engaging position alongside the mandrel, said comb having a series of thread-forming teeth thereon corresponding in number and spacing to the number of threads to be formed on the work piece and to the pitch of such threads, means on the comb engaging the cam for moving the comb axially with reference to the mandrel when the shaft is rotated, the

helical face on the cam being equal to the pitch of a single thread, and means for moving the comb out of work-engaging position.

5. A threading tool of the class described comprising a shaft having a work-holding mandrel thereon, means for turning the shaft, a cam on the shaft having a helical face, a thread-forming comb supported in work-engaging position alongside the mandrel, said comb having a series of thread-forming teeth thereon corresponding in number and spacing to the number of threads to be formed on the work piece and to the pitch of such threads, means on the comb engaging the cam for moving the comb axially with reference to the mandrel when the shaft is rotated, the helical face on the cam being equal to the pitch of a single thread, and spring means for yieldably resisting the endwise movement of the comb under the influence of said cam.

6. A threading tool of the class described comprising a shaft having a Work-holding mandrel thereon, means for turning the shaft, a cam on the shaft having a helical face, a thread-forming comb supported in work-engaging position alongside the mandrel, said comb having a series of thread-forming teeth thereon corresponding in number and spacing to the number of threads to be formed on the work piece and to the pitch of such threads, means on the comb engaging the cam for moving the comb axially with reference to the mandrel when th shaft is rotated, the helical face on the cam being equal to the pitch of a single thread, and means for shifting the relative position of said cam on said shaft.

7. A threading tool of the class described comprising a shaft having a Work-holding mandrel thereon, means for turning the shaft, a cam on the shaft having a helical face, a thread-forming comb supported in work-engaging position alongside the mandrel, said comb having a series of thread-forming teeth thereon corresponding in number and spacing to the number of threads to be formed on the Work piece and to the pitch of such threads, means on the comb engaging the cam for moving the comb axially with reference to the mandrel when the shaft is rotated, the helical face on the cam being equal to the pitch of a single thread, and means whereby the cam may be moved endwise on the shaft after one complete revolution to selectively extend the length of the thread being formed.

SEMON H. S'I'UPAKOFI' 

